textproduct: Rapid City

KEY MESSAGES

- There is a marginal risk (level 1 of 5) for isolated severe thunderstorms across northeastern WY this afternoon and evening. Main threats are hail and damaging winds.

- There is a slight risk (level 2 of 5) for scattered severe thunderstorms across northeastern WY and southwestern SD Friday. Main threats are large hail and damaging winds.

- Active weather continues through the weekend with near daily chances for showers and storms.

DISCUSSION

(Today Through Tuesday) Issued at 318 AM MDT Wed Jun 11 2025

06z sfc analysis depicts cold front draped across southern SD. A line of weak showers is moving across the western SD plains with a couple of showers along the SD/NE border producing a few lightning strikes. This wave pushes east through this morning with weak subsidence behind the wave settling over the CWA and a frontal boundary stalling out over the region. This subsidence should keep things dry for western SD through most of today. Smoke from wildfires in Canada will also settle back into the region today, especially across the western SD plains.

The next wave moves across the Rockies and into the Northern Plains later this evening into tonight. Corridor of 1000-1500 J/kg ML CAPE develops along the stalled out front as theta-e ridge builds over northeastern WY. Deep layer moisture will also support stronger convection than yesterday. Upper level winds aren't too strong so bulk shear will be the limiting factor with 0-6km bulk shear values at around 30-40kt for northeastern WY by this afternoon. However, the instability and shear should be enough to support an isolated wind and hail threat later this afternoon. Convection shifts east overnight as the main wave makes it into the region.

Frontal boundary pushes further southwest Thursday with cooler airmass moving into the region. A marked temperature gradient will set up over the CWA with highs in the mid 60s across the northern half of the CWA and highs in the 80s across the southern half. Things will gradually dry out from west to east as the wave exits the region, though diurnal instability over the Black Hills may support some afternoon showers on Thursday.

The frontal boundary will remain stalled out over the region through this weekend into next week with low level southerly flow advecting gulf moisture into the region in the vicinity of the front. This will potentially support rounds of severe weather over the weekend beginning on Friday when the first of many impulses riding along upper level WSW flow impacts the region. There is a slight risk (level 2 of 5) across northeastern WY and southwestern SD for Friday afternoon with large hail and damaging winds being the primary concerns.

AVIATION

(For the 12Z TAFS Through 12Z Thursday Morning) Issued At 445 AM MDT Wed Jun 11 2025

There is a chance for showers and storms (with associated LCL MVFR conditions and gusty and erratic winds) this afternoon and evening across northeastern WY into the Black Hills. This shower/storm activity will move east through the evening into tonight. Otherwise, VFR conditions largely expected through tonight. MVFR/IFR conditions may develop across the western SD plains into the Black Hills late tonight into early tomorrow morning.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.